- RECENT HEADLINES
- Scheduled downtime: Realuminising in September
- OPTICON Call for Proposals for Semester 2020A
- The Death Throes of a Stripped Massive Star
- 15th Anniversary Celebration
- LT helps discover huge nova "super-remnant" in another galaxy
- New Robotic Telescope website launched
- First observations in mid-infrared
- Quicklook upgrade
The Liverpool Telescope (LT) will be offline in late September – early October while we realuminise the primary mirror.
The planned timeline for realuminising is:
- Wed 18th Sep: Last night of observing before realuminisation
- Thu 19th Sep: Telescope strip-down begins
- Mon 23rd Sep: Mirror removed and sent to aluminising facility
- Thu 26th Sep: Mirror returns and reassembly begins
- Mon 30th Sep: Recommissioning begins
- ~Thu 3rd Oct: Robotic operation resumes
The mirror will be removed from the LT and taken to the nearby aluminising plant at the William Herschel Telescope (WHT). Removing the mirror involves taking off all of the LT's instruments and dismantling the back of the telescope. Once the mirror is realuminised and the telescope and instruments reassembled, the process of recommissioning begins. The whole procedure is therefore quite involved and takes about two weeks, from instrument removal to resumption of robotic operations on-sky.
The procedure is talked about in a little more detail in a previous article written when the mirror was realuminised in 2015. Some aspects are adapted below for convenience, but for the complete historical article see "LT maintenance: mirrors realuminised and throughput doubled" (5th August 2015).
Realuminisation is necessary because the reflective part of the mirror, an incredibly thin layer of aluminium on the mirror's glass body, degrades over time. Humidity and other contaminants, especially dust from the Sahara desert, chemically attack the aluminium layer and reduces its overall reflectivity. Periodic cleaning is not 100% perfect, and after several years it's eventually better to take that aluminium off and put a fresh layer on.
The LT's primary mirror is a precision-crafted disc of glass two metres in diameter and 20cm thick, weighing in at 1.3 tonnes. Realuminising such a large and heavy piece of sensitive equipment without scratching it, or causing any damage at all, is a complex procedure:
- The primary mirror is slid out from underneath the telescope in its mirror cell and immediately covered in lint-free tissue to protect it and prevent dangerous reflections
- It's then carefully lifted off the mirror cell into a special padded transit box, and hoisted out of the top of the open enclosure to a waiting lorry. The lorry slowly and carefully takes the mirror the 500 metres to the aluminising plant at the WHT
- At the WHT, the mirror's aluminium layer is carefully removed with powerful acids, washed and carefully dried to ensure not a speck of dust remains on the surface
- The mirror is then put in the WHT's aluminising vacuum chamber where a new layer of pure aluminium is carefully evaporated onto the surface. The new layer is as thin as gold leaf, about 350 aluminium atoms deep. It measures just 100 nanometres (0.0001 mm) thick, or 160,000 times thinner than kitchen foil.
- The mirror is repackaged and carefully transported back to the LT. There it is hoisted back through the open enclosure, unpacked, and refitted to the telescope.
As touched on above, once the LT's many instruments are refitted, emphasis then focusses on recommissioning the telescope. Over several days and nights the telescope's engineering, optical and computer systems are all checked to make sure it's running autonomously again. Once we're happy, robotic operations recommence and an announcement is made on this website.
Updates will be posted at the head of this article during realuminisation.
The latest call for proposals for telescopes supported by the OPTICON Trans-National Access programme for semester 2020A has just been released. The LT is one of the telescopes in this programme, and complete instructions on how to apply to OPTICON for time on the LT are given in the relevant parts of the call, presented below:
Liverpool Telescope IO:O background image of the field around the host galaxy, with inset showing closeup taken by Canada-France-Hawaii Telescope (CFHT). Position of supernova SN2018gep in its host galaxy is marked by the white crosshairs in the CFHT inset. Click image for bigger version.
Optical spectra of SN2018gep taken from the ground by the LT (highlighted in yellow) and other telescopes. Numbers next to spectra denote time elapsed in days since supernova. Click image for bigger version.
The Liverpool Telescope's SPRAT spectrograph obtained the first spectra of a broad-lined stripped-envelope supernova last year, just seven hours after discovery by the Zwicky Transient Facility (ZTF).
The SPRAT spectra contributed to the study of the supernova, named “SN2018gep”. The results of the study are presented in a recent paper by Ho et al submitted to the Astrophysical Journal, entitled “The Death Throes of a Stripped Massive Star: An Eruptive Mass-Loss History Encoded in Pre-Explosion Emission, a Rapidly Rising Luminous Transient, and a Broad-Lined Ic Supernova SN2018gep”.
The supernova was identified as a rapidly rising (1.3 mag/hr) and luminous transient, and was discovered extremely early in its evolution — within an hour of the shock breakout.
The robotic Liverpool Telescope (LT) is ideally suited to the follow-up of fast transients such as this one, and the first spectrum of SN2018gep was obtained with SPRAT. The authors believe this is the earliest-ever spectrum of a stripped-envelope SN, in terms of temperature evolution.
This was followed by an intensive spectroscopic monitoring campaign using telescopes from around the world.
A retrospective search through pre-explosion data showed emission in the days to weeks leading up to the event, which is the first definitive detection of precursor emission for a supernova of this class.
The authors of the paper conclude that the data are best explained by shock breakout in a massive shell of dense circumstellar material at large radii that was ejected in eruptive pre-explosion mass-loss episodes.
Artist's impression. Adapted (badly) by J. Marchant from free cake drawing released under Creative Commons CC0 at Pixabay.
This year the Liverpool Telescope celebrated 15 years of continuous robotic observation of the Universe. The telescope went robotic for the first time on 22nd April 2004 (see archive news item) and routine robotic operations began in December 2004 (see the Night Reports from that time for a bit of nostalgia). Since then the LT has been delivering high impact science by robotically observing the night sky from its home on the Canary Island of La Palma.
To mark this milestone, Liverpool John Moores University's Astrophysics Research Institute held a celebration on 24th April at nearby Sensor City in Liverpool. The evening brought together members of the LT team, past and present, to provide an exciting history from concept to construction with an insight into daily operation.
Prof Iain Steele talked about how and why the initial concept came about, the building of the telescope, and its first ever observation ("first light"). Dr Chris Copperwheat reviewed the impact on science that the LT has made over the years, and Dr Helen Jermak talked about the LT going into the future.
This is a composite image of Liverpool Telescope data (bottom left) and Hubble Space Telescope data (top right) of the nova super-remnant. M31N 2008-12a is in the middle of the image. Credit: Matt Darnley / LJMU.
An international team of astrophysicists have uncovered an enormous bubble currently being "blown" by the regular eruptions from a binary star system within the Andromeda Galaxy.
As reported in this week's Nature, recent observations with the Liverpool Telescope and Hubble Space Telescope, supported by spectroscopy from the Gran Telescopio Canarias, and the Hobby-Eberly Telescope (some of the largest astronomy facilities on Earth) discovered this enormous shell-like nebula surrounding ‘M31N 2008-12a’, a recurrent novae located in our neighbouring Andromeda Galaxy. At almost 400 lightyears across and still growing, this shell is far bigger than a typical nova remnant (usually around a lightyear in size) and even larger than most supernova remnants.
Dr Matt Darnley, lead author on the study and Reader in Time Domain Astrophysics at Liverpool John Moores University's Astrophysics Research Institute explains: “Each year ‘12a’ (as we lovingly refer to it) undergoes a thermonuclear eruption on the surface of its white dwarf. These are essentially hydrogen bombs, which eject material equivalent to about the mass of the Moon in all directions at a few thousand kilometres per second. These ejecta act like a snow plough, piling the surrounding ‘interstellar medium’ up to form the shell we observe – the outer ‘skin’ of the bubble, or the ‘super-remnant’ as we have named it.”
These new observations coupled with state-of-the-art hydrodynamic simulations (carried out at LJMU and the University of Manchester) have revealed that this vast shell is in fact the remains of not just one nova eruption but possibly millions – all from the same system.
Despite its uniqueness and staggering scale, the discovery of this super-remnant may have further significance.
Dr Matt Darnley continued: “Studying 12a and its super-remnant could help is to understand how some white dwarfs grow to their critical upper mass and how they actually explode once they gets there as a ‘Type Ia Supernova’. Type Ia supernovae are critical tools used to work out how the universe expands and grows.”
In a related work, also led by Matt Darnley, this team has predicted that 12a will ultimately explode as a Type Ia Supernova in less than 20,000 years – a very short time in cosmological terms.
Dr Rebekah Hounsell, second author on both studies and a post-doctoral researcher at the University of Pennsylvania, explains: “These are some of the largest explosions in the Universe (type Ia supernovae). Such an event in the Andromeda galaxy (M31) would be one of the closest supernovae observed by telescopes (the last one in M31 was in 1885 and in the Large Magellanic Cloud in 1987). The last one in our own galaxy (that we actually saw) was 1604. Although we’ve predicted that 12a will undergo a supernovae explosion in less than twenty thousand years – that sounds a long time, but of course that could still mean within the next decade or so.”
We have recently launched a new website for the Liverpool Telescope 2 or "New Robotic Telescope (NRT)" project. The webpages at www.robotictelescope.org detail the science case, NRT team and latest news items in relation to the new telescope.
The NRT team are currently preparing the Phase A design of the new 4-metre fully robotic and autonomous telescope, ready for a design board review in the Spring. The NRT will slew faster than the LT and be on target taking data within 30 seconds of trigger, allowing us to explore more rapidly fading targets.
The proposed location for the NRT is 400 metres from the LT on La Palma at the disused Carlsberg Meridian Telescope site, 100m from the William Herschel Telescope. There are also plans in place to repurpose the LT to support the scientific operations of the NRT and facilitate gravitational wave follow-up, along with facilitating a variety of new projects for the National Schools Observatory. The re-design of the LT is to allow a 2°×2° wide-field camera and a fibre-fed spectrograph as the main two instruments.
Keep an eye on the NRT website's latest news for updates on funding and design board reviews.
False-colour contrast-enhanced thermal image of part of the Moon's surface during a lunar eclipse. The bright patches are some of the many "hot spots" where the lunar soil was warmer than its surroundings. Credit & ©2019 Maisie Rashman, Iain Steele, LT Group.
The Liverpool Telescope (LT) recently made mid-infrared (mid-IR) images of the Moon during January's lunar eclipse. This was a first for the LT, which normally observes in the optical or near-infrared part of the spectrum.
Observing in this part of the spectrum is difficult because the telescope and instrument optics, plus the Earth's atmosphere itself, actually glow in this wavelength range — it's like trying to observe optically in the daytime with a luminous telescope. Astronomy in the mid-IR with ground-based telescopes is therefore a tricky process, normally involving cryogenically cooled instruments, and "chopping" and "nodding" techniques to rapidly alternate observations of the target with those of a blank patch of sky nearby. The latter signal is subtracted from the former to remove the extra signal from the atmosphere and equipment, leaving just the signal from the target.
By contrast, these observations were made as part of a project to see what data could be collected with an off-the-shelf uncooled thermal infrared microbolometer array camera, in this case a FLIR Tau 2 640, sensitive to the 7-14 micron wavelength range. These cameras are much cheaper than their cooled counterparts.
The observations began as the Moon entered the Earth's shadow and sunlight was progressively cut off from the lunar surface. Differences in thermal conductivity of the lunar regolith caused some places to cool at a slower rate than their surroundings, becoming apparent as many "hot spots" in the images.
Maisie Rashman, co-investigator in this experiment and a PhD student at Liverpool John Moores University's Astrophysics Research Institute, said "Once partial eclipse started we were able to see lots of small very bright, almost point, sources appear. Around the maximum, the temperature of the moon had dropped enough that the edge of the moon was almost indistinguishable."
This isn't the first time the Moon has been observed in mid-IR during an eclipse, but as LT Director Prof. Iain Steele says, it's "the first ever infrared image of an eclipse taken with a microbolometer array camera," and also the first time the LT has ventured into the mid-IR part of the spectrum.
The project was partly supported by a Royal Astronomical Society Patricia Tomkins grant.
The LT website's "Quicklook" page has had an upgrade. In keeping with the paradigm of "quick" in "quicklook", it's now possible to use a FITS viewer on the page to perform basic analysis in the browser itself, as well as examine the images in better detail than the JPEG without having to download the FITS file.